Francis runner and method for manufacture thereof

ABSTRACT

A Francis runner and a method for manufacture the same are provided in which the openings or notches are formed in the shroud ring in each water passage between the adjacent blades and in spaced apart relation therewith in order to facilitate the finishing of the inner surfaces of the water passages in the runner. The openings and notches are closed with the cover plates by welding after the finishing step has been completed in such a manner that the inner and outer surfaces of the cover plates may be in coplanar relation with those of the shroud ring. Thus, the finishing the inner surfaces of the long water passages in the Francis runners of water turbine or pump-turbine units with a high head or high lift and a slow specific speed having a long water passage length may be much facilitated.

United States Patent 1191 Hachiya et al.

[ Oct. 9, 1973 FRANCIS RUNNER AND METHOD FOR MANUFACTURE THEREOF [75 inventors: Takeo Hachiya; Susumu Naganuma; Tomotaka Umino,a1l of Hitachi-shi, Japan 11/1949 Great Britain 416/186 12/1953 Austria 416/186 Primary Examiner-Everette A. Powell, Jr. Attorney-Paul M. Craig, Jr. et al.

[57] ABSTRACT A Francis runner and a method for manufacture the same are provided in which the openings or notches are formed in the shroud ring in each water passage 416/186, 4l6/213i 5i/i1g/6di between the: qj blades fw in p apart rela [58] Fie'ld ll 86 21 tion therewlth in order to facilitate the finishing of the 29/1 inner surfaces of the water passages in the runner. The openings and notches are closed with the cover plates References Cited by welding after the finishing step has been completed in such a manner that the inner and outer surfaces of UNITED STATES PATENTS the cover plates may be in coplanar relation with 2,784,936 3/1957 Schmidt 416/186 those of the shroud ring. Thus, the finishing the inner 3,139,265 6/1964 Lindquist 416/186 surfaces of the long water passages in the Francis run- 3,608,172 9/1971 Lindquist 29/156.8 nets of water turbine pumpwrbine units with a FOREIGN PATENTS ()R APPLICATIONS high head or high lift and a slow specific speed having 580,119 8/1946 Great Britain 416/186 8 long Water Passage length may be much faclhtated- 8 Claims, 16 Drawing Figures PATENTED 9% 3,764,231

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PATENTED 91975 3.764.231

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SHEET 8 [1F 8 FRANCIS RUNNER AND METHOD FOR MANUFACTURE THEREOF BACKGROUND OF THE INVENTION The present invention relates to a Francis runner and a method for manufacture thereof.

The present trend of the pumped storage plants is toward the increased head with the greater capacity. In the Francis runner used in the hydroelectric power plants with a high head, the specific speed of the runner must be reduced so that the height of the blades is low. Further in the pump-turbine units in the pumped storage plants, the longer blades are used in order to increase the pumping efficiency.

In the Francis runner, the surfaces of the water passages defined generally by a crown ring, a shroud ring and a plurality of blades interposed therebetween must be finished as smoothly as possible. In the conventional method, the surfaces of the water passages are finished in access through the inlet or outlet end thereof after the shroud ring has been fabricated as a unitary construction. However, in case of the Francis runners of the type described above having long water passages defined by the complex curved surfaces, the finishing of the surfaces of the water passages becomes ex-' tremely difficult by the conventional methods.

SUMMARY OF THE INVENTION The primary object of the present invention is therefore to provide a highly efficient Francis runner and a method for manufacture thereof in which the difficulty of finishing the surfaces of the water passages of the runner may be eliminated.

According to one aspect of the present invention an opening is formed in a shroud ring in each water passage at a portion intermediate between the entrance and discharge edges of the shroud ring and between the adjacent blades in spaced apart relation therewith. Alternatively a notch or notches are formed in the shroud ring in each water passage on the side of the entrance or discharge edge or on both sides of the entrance and discharge edges of the shroud ring. The surface of each water passage may be finished through the opening or notch or notches, and after the finishing has been accomplished, the openings or notches are closed with the cover plates by welding in such a manner that the inner and outer surfaces of the cover plates may be placed in coplanar relation with those of the shroud ring.

According to another aspect of the present invention the openings or notches are closed with the inner and outer cover plates welded to the shroud ring. The inner cover plate whose inner surface is so finished as to match with the finished surface of the water passage closes the inner side of the opening or notch whereas the outer cover plate closes the outer side of the opening or notch.

According to the present invention, the finishing of the surfaces of the water passages of the Francis runner as well as the remedy of the defects caused in casting the component parts may be much improved. Hence, the highly efficient Francis runners may be manufactured in a simple manner.

The above and other objects, features and advantages of the'present invention will become more apparent from the following description of the preferred embodiments thereof taken in conjunction with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a fragmentary sectional view of a first embodiment of a Francis runner in accordance with the present invention;

FIG. 2 is a cross sectional view taken along the line "-11 of FIG. 1;

FIG. 3 is a fragmentary sectional view of a second embodiment of the present invention;

FIG. 4 is a cross sectional view taken along the line IVIV of FIG. 3;

FIG. 5 is a fragmentary sectional view ofa third embodiment of the present invention;

FIG. 6 is a cross sectional view thereof taken along the line VIVI of FIG. 5;

FIG. 7 is a fragmentary sectional view of a fourth embodiment of the present invention;

FIG. 8 is a cross sectional view thereof taken along the line VIII-VIII of FIG. 7;

FIGS. 9 and 10 illustrate a variation of the first embodiment shown in FIGS. 1 and 2;

FIGS. 11 and 12 illustrate a variation of the second embodiment shown in FIGS. 3 and 4;

FIGS. 13 and 14 illustrate a variation of the third embodiment shown in FIGS. 5 and 6; and

FIGS. 15 and 16 illustrate a variation of the fourth embodiment shown in FIGS. 7 and 8.

Same reference numerals are used to denote same component parts throughout the figures.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring first to FIG. 1, a Francis runner generally comprises a plurality of blades 12, a crown ring 14 and a shroud ring 16. The shroud ring 16 has a plurality of openings 18' formed therethrough in spaced apart relation with the blades 12 as shown in FIG. 2 so that the works required for finishing the surfaces of the water passages and correcting the defects caused in casting the component parts (which will be referred to as the finishing step" for brevity hereinafter) may be facilitated after the assembly. After the finishing step has been completed, cover plates 18 whose inner surfaces are so finished as to match with the finished inner surface of the shroud ring 16 are welded to close the openings 18 as indicated by the welded joints denoted by 10.

Next referring to FIGS. 3 and 4, the shroud ring 16 has a plurality of notches 20 formed therein in spaced apart relation with the blades 12 on the side of the discharge edge. As in the case of the first embodiment, after the finishing step, the cover plates 20 are welded to close the notches 20'.

In the embodiment shown in FIGS. 5 and 6, notches 22' are formed in spaced apart relation with the blades 12 on the side of the entrance edge. In the embodiment shown in FIGS. 7 and 8, the notches 20' and 22' are formed on both sides of the entrance and discharge edges.

In the variaton shown in FIGS. 9 and 10, the opening which are provided as in the case of the first embodiment (See FIGS. 1 and 2) are closed with inner cover plates 17 whose inner surfaces are finished to match with the finished inner surface of the shroud ring 16 and with outer cover plates 19 whose outer surfaces are so finished to match with the outer surface of the shroud ring 16. It will be of course readily understood that the inner cover plates 17 are welded first and then the outer cover plates 19 are welded.

In like manner in the variation shown in FIGS. 11 and I2, the notches are closed with inner and outer cover plates 21 and 23. In the variation shown in FIGS. 13 and 14, the notches are closed with inner and outer cover plates 27 and 29. In the variation shown in FIGS. and 16, the notches are closed with the inner and outer cover plates 21, 23; and 27 and 39. In variations illustrated in FIGS. 11 to 16, end plates 25 and 31 are welded to interpose between the inner and outer cover plates 2! and 23; and 27 and 29 respectively.

In variations illustrated in and described with reference to FIGS. 9l6, reinforcing rib members 24 may be welded as shown in FIGS. 9 and 10, and a plurality of small holes may be formed in the outer cover plates 19, 23 and 29 as shown in FIG. 11 in order to achieve the balance of pressures. I

In summary, according to the present invention, the openings or notches are formed in the shroud ring in order to facilitate the finishing step. After the finishing step has been completed, the cover plates whose inner surface are so finished as to match with the finished inner surface of the shroud ring are welded to close the openings or notches. Hence the present invention provides a method for manufacture of highly efficient Francis runners for water turbiner or pump-turbine units with a high head or a high lift but with a slow specific speed having a long water passage length.

What is claimed is l. A method for manufacturing a Francis runner having a long water passage comprising the steps of a. forming an opening in a shroud ring in each water passage between the adjacent blades in spaced apart relation therewith at a portion intermediate between the entrance and discharge edges of said shroud ring,

b. accomplishing the finishing step through said openings, and

c. closing said openings with cover plates by welding.

2. A method for manufacturing a Francis runner having a long water passage comprising the steps of a. forming a notch on the side of the entrance edge of a shroud ring in each water passage between the adjacent blades in spaced apart relation therewith,

b. accomplishing the finishing step through said notches, and

c. closing said notches with cover plates by welding.

3. A method for manufacturing a Francis runner having a long water passage length comprising the steps of a. forming a notch on the side of the discharge edge of a shroud ring in each water passage between the adjacent blades in spaced apart relation therewith,

b. accomplishing the finishing step through said notches, and

c. closing said notches with cover plates by welding.

4. A method for manufacturing a Francis runner having a long water passage comprising the steps of a. forming two notches on both sides of the entrance and discharge edges of a shroud ring in each water passage between the adjacent blades in spaced apart relation therewith,

b. accomplishing the finishing step through said notches, and

c. closing said notches with cover plates by welding.

5. In a Francis runner comprising a crown ring, a shroud ring, and a plurality of blades interposed therebetween to define a plurality of water passages extending in an inclined direction with respect to respective radii of the runner, an improvement comprising an inner cover plate welded to said shroud ring to close the inner side of an opening formed in said shroud ring in each water passage between the adjacent blades in spaced apart relation therewith at a portion intermediate between the entrance and discharge edges of said shroud ring,

the inner surface of said inner cover plate being placed in coplanar relation with the inner surface of said shroud ring, and

an outer cover plate welded to said shroud ring to close the outer side of said opening in coplanar relation with the outer surface of said shroud ring.

6. In Francis runner comprising a crown ring, a shroud ring, and a plurality of blades interposed therebetween to define a plurality of water passages extending in an inclined direction with respect to respective radii of the runner, an improvement comprising an inner cover plate welded to said shroud ring to close the inner side of a notch formed in said shroud ring on the side of the entrance edge thereof in each water passage between the adjacent blades in spaced apart relation therewith,

the inner surface of said inner cover plate being placed in coplanar relation with the inner surface of said shroud ring, an outer cover plate welded to said shroud ring to close the outer side of said notch in coplanar relation with the outer surface of said shroud ring, and

an end plate welded between said inner and outer cover plates to define the entrance edge of said closed notch.

7. In a Francis runner comprising a crown ring, a shroud ring, and a plurality of blades interposed therebetween to define a plurality of water passages extending in an inclined direction with respect to respective radii of the runner, an improvement comprising an inner cover plate welded to said shroud ring to close the inner side of a notch formed in said shroud ring on the side of the discharge edge thereof in each water passage between the adjacent blades in spaced apart relation therewith,

the inner surface of said inner cover plate being placed in coplanar relationwith the inner surface of said shroud ring, an outer cover plate welded to said shroud ring to close the outer side of said notch in coplanar relation with the outer surface of said shroud ring, and

an end plate welded between said inner and outer cover plates to define the discharge edges of said closed notch.

8. In a Francis runner comprising a crown ring, a shroud ring, and a plurality of blades interposed therebetween to define a plurality of water passages extending in an inclined direction with respect to respective radii of the runner, an improvement comprising inner cover plates welded to said shroud ring to close the inner sides of notches formed in said shroud ring on both sides of the entrance and discharge edges thereof respectively in each water passage between the adjacent blades in spaced apart relation therewith 6 shroud ring, and end plates welded between said inner and outer cover plates respectively to define the entrance and discharge edges of said closed notches respectively. 

1. A method for manufacturing a Francis runner having a long water passage comprising the steps of a. forming an opening in a shroud ring in each water passage between the adjacent blades in spaced apart relation therewith at a portion intermediate between the entrance and discharge edges of said shroud ring, b. accomplishing the finishing step through said openings, and c. closing said openings with cover plates by welding.
 2. A method for manufacturing a Francis runner having a long water passage comprising the steps of a. forming a notch on the side of the entrance edge of a shroud ring in each water passage between the adjacent blades in spaced apart relation therewith, b. accomplishing the finishing step through said notches, and c. closing said notches with cover plates by welding.
 3. A method for manufacturing a Francis runner having a long water passage length comprising the steps of a. forming a notch on the side of the discharge edge of a shroud ring in each water passage between the adjacent blades in spaced apart relation therewith, b. accomplishing the finishing step through said notches, and c. closing said notches with cover plates by welding.
 4. A method for manufacturing a Francis runner having a long water passage comprising the steps of a. forming two notches on both sides of the entrance and discharge edges of a shroud ring in each water passage between the adjacent blades in spaced apart relation therewith, b. accomplishing the finishing step through said notches, and c. closing said notches with cover plates by welding.
 5. In a Francis runner comprising a crown ring, a shroud ring, and a plurality of blades interposed therebetween to define a plurality of water passages extending in an inclined direction with respect to respective radii of the runner, an improvement comprising an inner cover plate welded to said shroud ring to close the inner side of an opening formed in said shroud ring in each water passage between the adjacent blades in spaced apart relation therewith at a portion intermediate between the entrance and discharge edges of said shroud ring, the inner surface of said inner cover plate being placed in coplanar relation with the inner surface of said shroud ring, and an outer cover plate welded to said shroud ring to close the outer side of said opening in coplanar relation with the outer surface of said shroud ring.
 6. In Francis runner comprising a crown ring, a shroud ring, and a plurality of blades interposed therebetween to define A plurality of water passages extending in an inclined direction with respect to respective radii of the runner, an improvement comprising an inner cover plate welded to said shroud ring to close the inner side of a notch formed in said shroud ring on the side of the entrance edge thereof in each water passage between the adjacent blades in spaced apart relation therewith, the inner surface of said inner cover plate being placed in coplanar relation with the inner surface of said shroud ring, an outer cover plate welded to said shroud ring to close the outer side of said notch in coplanar relation with the outer surface of said shroud ring, and an end plate welded between said inner and outer cover plates to define the entrance edge of said closed notch.
 7. In a Francis runner comprising a crown ring, a shroud ring, and a plurality of blades interposed therebetween to define a plurality of water passages extending in an inclined direction with respect to respective radii of the runner, an improvement comprising an inner cover plate welded to said shroud ring to close the inner side of a notch formed in said shroud ring on the side of the discharge edge thereof in each water passage between the adjacent blades in spaced apart relation therewith, the inner surface of said inner cover plate being placed in coplanar relation with the inner surface of said shroud ring, an outer cover plate welded to said shroud ring to close the outer side of said notch in coplanar relation with the outer surface of said shroud ring, and an end plate welded between said inner and outer cover plates to define the discharge edges of said closed notch.
 8. In a Francis runner comprising a corwn ring, a shroud ring, and a plurality of blades interposed therebetween to define a plurality of water passages extending in an inclined direction with respect to respective radii of the runner, an improvement comprising inner cover plates welded to said shroud ring to close the inner sides of notches formed in said shroud ring on both sides of the entrance and discharge edges thereof respectively in each water passage between the adjacent blades in spaced apart relation therewith the inner surfaces of said inner cover plates being placed in coplanar relation with the inner surface of said shroud ring, outer cover plates welded to said shroud ring to close the outer sides of said notches respectively in coplanar relation with the outer surface of said shroud ring, and end plates welded between said inner and outer cover plates respectively to define the entrance and discharge edges of said closed notches respectively. 